There are several methods for assessment of antioxidant activity, of which DPPH scavenging assay. DPPH has absorbance around 520nm, while carotenoids have absorbance near 500nm.
Dear Hussein,
Considering the methods used in antioxidant activity assays, they were divided in hydrogen atom transfer (HAT) and single electron transfer (SET). HAT-based methods measure the capacity of an antioxidant to trap free radicals by hydrogen donation, while SET methods rely on the one electron transfer reductive ability of an antioxidant compound versus a radical species. ORAC, TRAP, and chemiluminescence are HAT methods, whereas FRAP and CUPRAC are SET methods. DPPH and ABTS (TEAC) methods were regarded as HAT and SET methods.
The carotenoids are known to react as antioxidant compounds through two mechanisms: the SET and HAT. In general, the antioxidant properties of carotenoids are related more to their high capacity for electron donation (SET).
So, both DPPH and ABTS methods are appropriate for the determination of antioxidant activity assay of carotenoids.
Best wishes
Duried
Yes, the presence of carotenoids you very likely interfere in the assay. To account for this, you need to set appropriate blank/control assays, mixing the samples with the solvent used to solubilize the DPPH (usually methanol or ethanol). Then, you just subtract it from the "complete" assay.
DPPH absorbs light at > 550 nm, while beta-carotene not. Measure the consumption of DPPH at wavelength > 600 nm
It's better to try different method to assay antioxidant activity.. hydroxyl radicals scavenging activity may help more than dpph
Mohammed Najim Abed Carotenoids are not soluble in water. What is a life time of the hydroxyl radical in organic medium? How you can scavenge HO(.) in organic solvent? We all need to be responsible for what we are suggesting.
@Yurii V Geletii
Carotenoids are able to scavenge hydroxyl radicals by using ESR. Actually you are right, ''We all need to be responsible for what we are suggesting''.
Mohammed Najim Abed How can you scavenge hydroxyl radicals by using ESR? Hydroxyl radical reacts with almost all organic solvent molecules with a diffusion controlled rate constants. Carotenoids do not have any chance to compete for the hydroxyl radicals due to a simple reason: the concentration of solvent molecules is much higher than carotenoids. Another question is how to cleanly generate hydroxyl radicals? I don't know any protocol to look at the reactions of hydroxyl radicals with carotenoids in organic solvents.
l reacts
(@Yurii V Geletii) you can just need to read more about it.
Regards
Mohammed Najim Abed Your last post is a personal attack. You must follow rules of scientific discussions. I claim that carotenoids can't scavenge hydroxyl radicals in organic solvents. Pls, disprove or prove opposite.
No one is perfect and we all need to read and learn new things every day. If anyone revise your first comment to me will notice the real attack, insultation and breaching the rules of scientific discussion on researchgate. I respect your opinion but I am not used to this way of communication so let me stop the discussion at this point @ Yurii V Geletii
Dear Muhammad Bilal Tahir
. I recommended your post feeling that I could be too straightforward. I would like to learn from you how I insulted the research community in this discussion? What was the "harsh" way in my answer to the original question? Actually I gave the best answer. Mohammed Najim Abed gave his own advise. I had doubt that it could work and asked several legitimate questions without any attempt to discredit him. Instead of answering he advised me to read more which is actually statement of my incompetence in this area. Where I breached the rules of scientific discussion? Mohammed Najim Abed wrote "I am not used to this way of communication ." What was wrong in my posts? The answer to your advise to read more? I don't know many things, please, teach me, answer my questions and defend your proposal.
Hi Hussein H. Al-Turnachy. I wanna know if you solved that problem and what did you do? I´m with the same problem! Any information could help me, thanks so much!!
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